Revert "dev-lang/ruby: stable 2.3.6 for ppc, bug #639476"

This reverts commit f766749.

Breaks dependency tree. See
https://qa-reports.gentoo.org/output/gentoo-ci/75e30ab24/output.html#dev-lang/ruby

dev-lang/ruby/ruby-2.3.6.ebuild

@@ -30,7 +30,7 @@ SRC_URI="mirror://ruby/${SLOT}/${MY_P}.tar.xz
  https://dev.gentoo.org/~flameeyes/ruby-team/${PN}-patches-${PATCHSET}.tar.bz2"
 
 LICENSE="|| ( Ruby-BSD BSD-2 )"
-KEYWORDS="~alpha amd64 ~arm ~arm64 ~hppa ia64 ~mips ppc ~ppc64 ~s390 ~sh sparc x86 ~amd64-fbsd ~x86-fbsd"
+KEYWORDS="~alpha amd64 ~arm ~arm64 ~hppa ia64 ~mips ~ppc ~ppc64 ~s390 ~sh sparc x86 ~amd64-fbsd ~x86-fbsd"
 IUSE="berkdb debug doc examples gdbm ipv6 jemalloc libressl +rdoc rubytests socks5 ssl tk xemacs ncurses +readline"
 
 RDEPEND="